Osteoarthritis is the most common form of arthritis, affecting 25 to 35 million people in the U.S. Chronic pain and disability of osteoarthritis is initially caused by inflammatory responses in joint cartilage and bone that gradually worsens over time. Symptomatic osteoarthritis of the knee occurs in 10 to 13% of persons aged 60 and over. Knee osteoarthritis alone increases the risk of loss of mobility, such as needing assistance walking or climbing stairs, greater than for any other medical condition in people aged 65 and over.
Current drug treatment for osteoarthritis of the knee is limited to analgesics, nonsteroidal anti-inflammatory drugs (NSAIDs) and intra-articular steroid injections, all of which have significant limitations due to adverse effects. Despite these medical treatments, chronic knee osteoarthritis often causes progressive disability requiring total joint replacement. The increasing prevalence of osteoarthritis of the knee due to aging and obese populations suggests a growing clinical need for safe and effective local knee treatments that will delay and potentially eliminate the need for more extensive surgical treatments.